Meteorologist Predicts Atlantic Cooling

Something significant is occurring in the Atlantic Ocean, according to meteorologist Paul Dorian of US weather forecast service Vencore Weather - Atlantic cooling. This graph shows the observed Atlantic Multidecadal Oscillation index, for the period 1870-2015. Courtesy: NCAR

Something significant is occurring in the Atlantic Ocean, according to meteorologist Paul Dorian of US weather forecast service Vencore Weather – Atlantic cooling. Evidence is growing to support predictions that the Atlantic Ocean is in a cooling phase and is set to cool further over coming decades with weather impacts for northern Europe and the north western US. Dorian is not the first scientist to reach this conclusion and he has put his thoughts into this article which was posted on the Vencore Weather website.

by Paul Dorian, Meteorologist, Vencore, Inc.

Overview
In addition to solar cycles, temperature cycles in the planet’s oceans play critical roles in our ever changing climate and also on the extent of global sea ice. Oceanic temperature cycles are often quite long-lasting and a warm or cold phase can persist for two or three decades at a time. In general, the Atlantic Ocean experienced a cold phase from the early 1960’s to the mid 1990’s at which time it flipped to a warm phase and that has continued for the most part ever since. The current warm phase; however, is now showing signs of a possible long-term shift back to colder-than-normal sea surface temperatures (SST) and this could have serious implications on US climate and sea ice areal extent in the Northern Hemisphere.

Recent temperature trends in the Atlantic Ocean
The comparison chart (above) of SST anomalies between August 2014 (top) and today (bottom) shows a big drop in temperatures across much of the northern Atlantic Ocean. The rather limited colder-than-normal (blue) patches from August 2014 have increased noticeably in areal extent when compared to the most recent measurements. Also, the well above-normal waters (orange) of August 2014 that existed east and south of Greenland have cooled off dramatically during this time period and there has even been a switch from well above-normal (orange) to below-normal (blue) in sections.

Long-term temperature trends in the Atlantic Ocean
On a longer time scale, there is supporting evidence from the National Oceanographic Data Center that something significant is indeed occurring in the Atlantic Ocean. Since around early 2007, there has been a definitive downward trend in “monthly heat content anomaly” in the top 700 meters of the northern Atlantic Ocean (arrow region). The heat content in this part of the Atlantic Ocean ramped up rather sharply beginning around the middle 1990’s and seemingly peaked during early 2007.

Global monthly heat content anomaly (GJ/m2) in the uppermost 700 m of the North Atlantic since January 1955. The thin line indicates monthly values and the thick line represents the simple running 37 month (c. 3 year) average. Data source: National Oceanographic Data Center (NODC), climate4you.com. Last period shown: October-December 2015.

Atlantic Multidecadal Oscillation (AMO)
One way meteorologists can monitor sea surface temperature patterns in the North Atlantic Ocean is through an index value known as the Atlantic Multidecadal Oscillation (AMO). Positive (negative) phases of the AMO coincide with warmer (colder) North Atlantic sea surface temperatures. The AMO is linked with decadal climate fluctuations such as European summer precipitation, Atlantic hurricanes and variations in global temperatures. The monthly values for the AMO index are shown in the plot below for the period of 1870-2015 where positive values (reds) represent warmer-than-normal time periods and negative values (blues) indicate cold phases. Sea surface temperature cycles have tended to last for two or three decades at a time before phase changes take place. The last major phase change (cold-to-warm) took place right around the mid-point of the 1990’s (arrow). The AMO index appears to have reached a peak in this current (warm) phase during the latter part of last decade and it has generally been descending during the past few years providing support to the notion that a cool-down is indeed occurring in the North Atlantic.

Computer model forecast for Atlantic Ocean sea surface temperatures
One indication that this apparent downward trend in Atlantic Ocean sea surface temperatures will indeed have some staying power comes from the Japan Agency for Marine-Earth Science and Technology (JAMSTEC). JAMSTEC’s global seasonal forecasting of sea surface temperature anomalies has a pretty good track record and its most recent long-range forecast (below) suggests there will be a fairly widespread area of colder-than-normal water in the northern Atlantic Ocean during the winter season of 2016-2017 (circled blue region).

Ramifications on Northern Hemisphere sea ice areal extent
If the Atlantic Ocean is indeed slipping back into a colder-than-normal phase (i.e., negative AMO) then this would quite likely have a significant impact on Northern Hemisphere (NH) sea ice areal extent. The NH sea ice areal extent was generally at above-normal levels before the middle 1990’s (arrow in plot below) which is when the Atlantic Ocean temperature phase change took place from cold-to-warm. Once the warm phase of the Atlantic Ocean became established in the late 1990’s, the NH sea ice areal extent trended sharply downward from positive levels into well below-normal territory. In recent years, there has been a jagged, but generally sideways trend in NH sea ice areal extent at those well below-normal levels. However, if these recent signs of a possible long-term Atlantic Ocean temperature phase change from warm-to-cold are real and sustained (sometimes there are false starts), then the NH sea ice areal extent will very likely return to above-normal levels in the not too distant future – just as it was during the last cold phase pre-mid 1990’s.

Potential ramifications of an Atlantic Ocean temperature shift on US Climate
The largest body of water in the world by far is the Pacific Ocean and it is well understood that its temperature cycles play a critically important role in weather and climate not only in the US, but throughout the world. While the Atlantic Ocean is far smaller than the Pacific Ocean, its temperature cycles can also play an important role in the US for weather and climate. In an effort to investigate the possible impact of Atlantic Ocean temperature cycles on US climate, wintertime (DJF) temperature anomaly maps were generated for two distinct twenty-year periods. The first period is 1975-1995 which generally featured a cold phase in the Atlantic Ocean and the second period encompasses the current warm phase period of 1995-2015. The differences in wintertime US temperature anomalies are quite dramatic for these two twenty-year periods. The cold phase from 1975-1995 featured colder-than-normal winters on average throughout the US whereas in the recent 20-year warm phase period of 1995-2015, the opposite took place with virtually nationwide warmer-than-normal winters. No doubt many other important factors played a role in the weather conditions during the past forty winter seasons (e.g., El Nino/La Nino), but these dramatic differences in US temperatures that took place during different phases of the Atlantic Ocean suggest it is definitely something to monitor closely over the next several years.

1 Commenton "Meteorologist Predicts Atlantic Cooling"

I find this “looking at the recent past” article enough out of date that I wonder about its usefulness. Arctic Ocean temperatures remained unusually warm all this winter (beginning in December) and continue to show enormous spikes of anomalous warmth, as well as considerable areas of missing sea ice (especially east of Svalbard, from December onward) which only two years ago were present until April.

Also, your comfortable inter-changing of “Atlantic Ocean” and “north Atlantic” as if they are the same thing is at best confusing to the reader, and gives misleading impressions. The mid-latitude Atlantic is warmer because a normally bottom-hugging salty-cold Labrador Current is instead hugely freshened by prematurely melting Greenland ice, keeping at the surface sufficiently that it clashes wildly with the Gulf Stream… which has turned southward compared to its usual course. Instead of going directly toward Ireland the Gulf Stream now heads for Spain and west Africa – greatly and anomalously warming those equatorial waters.

The resulting “cold blob” between Greenland and Scotland is an area no longer warmed by the Gulf Stream… but nonetheless excessive surface air warmth from Norway northward (sometimes as much as 15°C warmer than typical) in concert with warmer Arctic waters from the Barents Sea northward is not only sharply reducing ice cover, but also activating 1000’s of new seafloor methane seeps… as the warmer surface water is overturned down to the depths.

All in all, your hypothesis seems founded upon a narrowly sampled (and perhaps selectively sampled) data sets. Why, for instance do you compare April SST’s from one year with August SSTs another year? Any *one* day may give you the conclusion you’d like us to adopt, but an average of winter months 2015-2016 weighted against similar months from, say 2005-2006 will blow holes in your conclusion.